Honey is one of the oldest sweeteners consumed by humans, with recorded use as far back as 5,500 BC. It’s also rumored to have special, long-lasting properties.
Many people have heard of jars of honey being unearthed in ancient Egyptian tombs, still as good to eat as the day they were sealed.
These stories have led many people to believe that honey simply doesn’t go bad, ever.
But is that really true?
This article investigates why honey can last so long, and what can cause it to go bad.
Honey is a sweet, natural substance produced by bees from the nectar or secretions of plants (1,
The bees suck flower nectar, mix it with saliva and enzymes and store it in a honey sack. Then they leave it in the hive to ripen and be used as food (
Because the composition of honey depends on the species of the bees as well as the plants and flowers they use, it can vary significantly in flavor and color, from clear and colorless to dark amber (1).
Honey is made up of approximately 80% sugar and no more than 18% water. The exact amount is determined by the bee species, plants, weather and humidity as well as processing (1).
It also contains organic acids such as gluconic acid, which is responsible for its characteristic acidic taste. Additionally, the pollen found in unfiltered honey contains very small amounts of protein, enzymes, amino acids and vitamins (1).
Nutritionally, the only significant nutrient in honey is sugar, with 17.2 grams and 65 calories per tablespoon (21 grams) (3).
There are also traces of minerals, such as potassium, particularly in darker varieties, though the amounts are too small to be nutritionally relevant (1).
Honey is a food produced by bees from the nectar of plants. It’s high in sugar and contains trace amounts of other substances such as organic acids, potassium, proteins, enzymes and vitamins.
Honey has a few special properties that help it last a long time, including a high sugar and low moisture content, an acidic nature and antimicrobial enzymes produced by bees.
It Is Very High in Sugar and Low in Moisture
Honey is made up of about 80% sugar, which can inhibit the growth of many types of microbes such as bacteria and fungi (
A high sugar content means that the osmotic pressure in honey is very high. This causes water to flow out of the cells of microbes, stopping their growth and reproduction (
In addition, despite containing around 17–18% water, the activity of water in honey is very low (
This means that the sugars interact with the water molecules so they cannot be used by microorganisms and no fermentation or breakdown of honey can occur (
Additionally, as honey is quite dense, oxygen cannot easily dissolve into it. This, again, prevents many types of microbes from growing or reproducing (
It Is Acidic
The pH of honey ranges from 3.4 to 6.1, with an average pH of 3.9, which is quite acidic. The primary reason for this is the presence of gluconic acid, which is produced during nectar ripening (
Originally, it was thought that the acidic environment of honey was responsible for preventing microbial growth. However, studies comparing varieties with lower and higher pH values did not find a significant difference in antimicrobial activity (5).
Nonetheless, for certain bacteria such as C. diphtheriae, E.coli, Streptococcus and Salmonella, an acidic environment is certainly hostile and hinders their growth (5).
In fact, honey is so effective in killing certain types of bacteria that it’s even used on burn wounds and ulcers to prevent and treat infections (
Bees Have Special Enzymes That Suppress Bacterial Growth
During honey production, bees secrete an enzyme called glucose oxidase into the nectar to help preserve the honey (1, 5).
As the honey ripens, glucose oxidase converts sugar into gluconic acid and also produces a compound called hydrogen peroxide (5).
This hydrogen peroxide is thought to contribute to the antibacterial properties of honey and help prevent the growth of microorganisms (1,
In addition, honey has been found to contain a variety of other compounds such as polyphenols, flavonoids, methylglyoxal, bee peptides and other antibacterial agents, which may also add to its antimicrobial qualities (
Honey has high sugar and low moisture content. It’s acidic and contains the antibacterial substance hydrogen peroxide. These three features are what allows properly stored honey to keep for so long.
Despite honey’s antimicrobial properties, it can go off or cause sickness under certain circumstances. These include contamination, adulteration, incorrect storage and degradation over time.
It May Be Contaminated
The microbes naturally present in honey include bacteria, yeast and molds. These can come from pollen, the bees’ digestive tract, dust, air, dirt and flowers (
Due to honey’s antimicrobial properties, these organisms are usually only found in very small numbers and are unable to multiply, which means they should not be a health concern (
However, spores of the neurotoxin C. botulinum are found in 5–15% of honey samples in very small amounts (
This is generally harmless for adults, but babies under the age of one can, in rare cases, develop infant botulism which can cause damage to the nervous system, paralysis and respiratory failure. Therefore, honey is not suitable for this young age group (
Additionally, a large number of microorganisms in honey could indicate secondary contamination during processing from humans, equipment, containers, wind, dust, insects, animals and water (
It Can Contain Toxic Compounds
When bees collect nectar from certain types of flowers, plant toxins can be transferred into the honey (
A well-known example of this is “mad honey,” caused by grayanotoxins in nectar from Rhododendron ponticum and Azalea pontica. Honey produced from these plants can cause dizziness, nausea and problems with heart rhythm or blood pressure (
Additionally, a substance known as hydroxymethylfurfural (HMF) is produced during the processing and aging of honey (
While some research has found negative effects of HMF on health such as damage to cells and DNA, other studies also report some positive features such as antioxidative, anti-allergy and anti-inflammatory properties (
Nevertheless, it’s recommended that finished products contain no more than 40 mg of HMF per kilogram of honey (
It May Be Adulterated
Honey is an expensive, time-consuming food to produce.
As such, it has been the target of adulteration for many years. Adulteration refers to adding cheap sweeteners to increase volume and reduce costs.
To cheapen production, bees can be fed with sugar syrups from maize, cane and beet sugar or sugar syrups could be directly added to the finished product (14, 15).
Additionally, to speed up processing, honey may be harvested before it’s ripe, resulting in a higher and unsafe water content (15).
Normally, bees store honey in the hive and dehydrate it so that it contains less than 18% of water. If honey is harvested too early the water content can be over 25%. This results in a much higher risk of fermentation and bad taste (15).
It May Be Stored Incorrectly
If honey is stored incorrectly it can lose some of its antimicrobial properties, become contaminated or start to degrade.
When it’s left open or improperly sealed, the water content may start to rise above the safe level of 18%, increasing the risk of fermentation.
In addition, open jars or containers can allow honey to become contaminated with microbes from the surrounding environment. These could grow if the water content becomes too high.
Heating honey at high temperatures can also have negative effects by speeding up the degradation of color and flavor as well as increasing the HMF content (16).
It Can Crystallize and Degrade Over Time
Even when stored correctly, it’s quite normal for honey to crystallize.
That’s because it contains more sugars than can be dissolved. It doesn’t mean it has gone bad but the process does cause some changes (1).
Crystallized honey becomes whiter and lighter in color. It also becomes much more opaque instead of clear, and may appear grainy (1).
It is safe to eat. However, water is released during the crystallization process, which increases the risk of fermentation (1, 17).
Additionally, honey stored for a long time may become darker and start to lose its aroma and flavor. While this is not a health risk, it may not be as tasty or attractive.
Honey can go bad when it’s contaminated, if bees collect nectar from certain toxic plants and if it’s adulterated or stored incorrectly. Crystallization is a naturally occurring process and generally does not mean your honey has gone bad.
To make the most out of your honey’s long-lasting properties, it’s important to store it correctly.
A key factor for storage is moisture control. If too much water gets into your honey, the risk of fermentation increases and it may go bad.
Here are some tips on best storage practices (18):
- Store in an airtight container: Store-bought jars or bottles, glass jars and stainless-steel containers with airtight lids are suitable.
- Keep in a cool, dry area: Honey should ideally be stored below 50°F (10°C). However, storing it at cool room temperatures between 50–70 °F (10–20°C) is generally ok.
- Refrigeration: Honey can be kept in the refrigerator if preferred but it may crystallize faster and become denser.
- Warm if crystallized: If honey crystallizes, you can return it to liquid form by gently warming and stirring it. However, do not overheat or boil it as that will degrade its color and flavor.
- Avoid contamination: Avoid contaminating honey with dirty utensils such as knives or spoons, which could allow bacteria, yeasts and molds to grow.
- If in doubt, throw it out: If your honey tastes off, is foamy or you notice a lot of free water, it may be best to throw it out.
Remember that different types of honey may look and taste different. For specific storage instructions, refer to the ones printed on the label of your individual product.
Honey should be kept in an airtight container in a cool, dry area. It is most important to limit the amount of moisture that can get into the container as a higher water content increases the risk of fermentation.
Honey is a delicious, sweet food that comes in many different flavors and colors depending on where it’s produced.
Due to its high sugar and low water content, as well as its low pH value and antimicrobial properties, honey may stay fresh for years, decades or even longer.
However, under certain circumstances, it may go bad or lose its appeal.
Honey may be contaminated by bacteria, yeasts, fungi or molds, though they usually will not reproduce to significant numbers. It may also contain toxic compounds from certain plants or can be adulterated with poor-quality sweeteners or processing.
Additionally, honey that is stored incorrectly will not last as long. Therefore, it’s important to keep it sealed in an airtight container in a cool, dry place.
By purchasing honey from reputable suppliers and storing it correctly, it can be enjoyed safely for many years on end.